At the same time, the pace of emissions from burning fossil fuels continues to grow at a high rate.

Executive-Director of the Global Carbon Project (GCP) and co-author of the 2014 report CSIRO's Dr Pep Canadell said the carbon dioxide level was "unprecedented in human history".

Dr Canadell said fossil fuel carbon dioxide emissions are projected to increase 2.5 per cent this year, bringing the total carbon dioxide emissions from all sources above 40 billion tonnes.

"Fossil fuel emissions in the past 10 years on average grew at 2.5 per cent per year, lower than the growth rate in the 2000s (which was 3.3 per cent per year) but higher than the growth rate in the 1990s (1 per cent)," Dr Canadell said.

"The declining growth rate in recent years is associated with lower GDP growth compared to the 2000s, particularly in China."

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